Method of making lead-copper particles



Patented July 12, 1927.

UNITED STATES PATENT OFFICE.

HARRY M. WILLIAMS, 0F DAYTON, OHIO, ASSIGNOR T0 GENERAL MOTORS RESEARCH CORPORATION', A CORPORATION 0F DELAWARE.

METHOD MAKING LEAD-COPPER PARTICLES.

Application med 'July 22, 1925. serial No. 45,285.

This invention relates to the art of making fine particles of an alloy, or homogeneous mixture, by atomizing a molten mixture of desired metals.

The usual method of making alloys, is to mix the metallic ingredients in a molten condition and allow them to harden. By this method, articles may be made of an alloy,

-or homogeneous mixture of metals, the ingredicnts of which are metals that are soluble one in another. This method is not well adapted to making mixtures of metals that are not soluble or miscible, one in another, at alltemperatures. Alloys of the latternamed class of metals would be extremely useful for many purposes, if they could be commercially produced. Homogeneous mixtures, for example, of nickel and lead, copper and lead, andI of many other V metals, not readily made by the usual method, can be produced by the method of this inventlon. In this invention it is proposed to mix metals which do not alloy or only partially alloy when cold, but which are miscible when in a molten condition. Copper and lead, for example, will mix intimately at certain high temperatures, but will separate out at the temperature at which the copper freezes or sets, so that, if copper and lead are mixed together in a molten condition, the lea'd will segregate out and form a layer at the bottom iof the copper as the melt solidies.

In the method which forms thesubject of this application, molten copper and lead, for

' example, are poured into acrucibe having a nozzle through which the molten metal will flow. The flowing molten meta-l, while maintained at a temperature above that at which the metals separate, is then atomized. The resulting tine particles are found to be a homogeneous mixture of pure lead and copper. The particles cool so rapidly after they have been atomized, that there is no 0pportunity for oxidation to take place, and

' no opportunity for the lead to Sepa-rate.

The accompanying drawings illustratean apparatus which may be used for producing copper and lead, or other homogeneous mixtures, of the class under consideration.

Fig. 1 is a cross-section through a portion of a furnace, Crucible and atomizing nozzle;

and

Fig. 2,' is a section on the line 2-2 of Fig. 1, the parts being viewed from beneath.

In the drawings, 10 indicates a combustion furnace adapted to be heated by gas lead into it through a pipe (not shown). This furnace may be made of fire brick, or other refractory material 11, built up within a iron, or preferably of high-heat-resisting.

alloy, such as nichrome.

Seated on the bottom plate 17, is a crucible 20, the lower end of which has a hole registering with the opening 18. Fastened in the hole of the Crucible, as by screw threads 21, is a nozzle 22, the lower end of which projects below the Crucible and the upper portion of which projects upward into the Crucible. The said lower end tapers, and

is provided with a narrow axial orifice,

which terminates in a counterbore 23 within the nozzle. The upper end of the nozzle is closed, as by a plug 24, shown in this case as screw-threaded into the upper end of the nozzle. The small perforation in the lower end of the nozzle is lined by a quartz tube 25, which projects below the lower end of the nozzle. The Crucible and nozzle may be made of any suitable refractory material, such as graphite. Above the lower end of the chamber within the Crucible, the nozzle 23 is provided with perforations, as at 26. These perforations serve to strain the meta-l that flows fromvthe Crucible into the nozzle, to free it from dross, slag, etc., which might otherwise cause an obstruction in the quartz tube 25. The lowerend of the graphite nozzle 22 ,is encased by a metallic shell 27, wlich mechanically strengthens its tapering en Attached to the underside of the bottom plate 17, is a member 28, which forms portion of an annular nozzle to eject aeriform fluid for the purpose of atomizing metal 1ssuing from the quartz tube 25. For convenience` the said annular nozzle may be called an air nozzle. 'llie inner portion of the air nozzle is formed by a metallic member 29, which conforms substantially to the form of the member 2T, and is spaced therefrom far enough so that there will be no binding of the parts, due to warping or expansion, under the iniluence of heat to which these parts are subjected. Tubes 30 conduct aeriform Huid from a. source of pressure (not shown) into the space between the members 28 and 29, so thatI the aeriform Huid may issue through the circular opening 3l at high speed in a hollow converging stream, which has an entraining effect upon the metal issuing through the quartz tube 25, and atomizes the said metal. Surrounding the nozzles is a casing 32, that has perforations in its walls to admit the tubes 30, and also a bottom opening 33 to permit the exit of metal and the atomizing stream. The air nozzle and the casing 32 may be clamped to the bottom plate 17, by means of bolts 3-1 and nuts 35. The metallic parts 27, 28 and 2S), may be made of some high-heat-resisting metal. The metal known commercially as Resistal has been found suitable for the purpose. Casing 32 should also be made of' some high-heat-resisting metal, such as Resistal, or an alloy sold under the name of .Ascoloy. Resistal is the trade name of an alloy containing G5 to 45 percent of iron, to 27.5 percent chromium, and from 20 to 3G percent nickel, respectively, and a smaller percentage of silicon and carbon. Ascoloy is the trade name for a chromiumiron alloy containing about 14 percent chromium. l

ln carrying out this method, combustion should be started in the furnace l0, before conducting met-al to the crucible 20, in order to heat the crucible and the nozzles, so that they will be at a sufliciently high temperature when the metal is poured into the erucible. The copper and lead, or other two metals, to be alloyed or made into homogeneous solid particles, are melted together, and the melted metals brought to a` temperature at which they are thoroughly miscible. rlhe mixture while at or above the temperature at which the metals intimately mix, is

lpoured into the Crucible 20. It fiows into the counterbore 23 of nozzle 22, through the orifices 26, and out through the quartz tube 25. An aeriform fluid under pressure, in this case air, is lead through the tubes 30 into the atomizing nozzle, whence it issues iu a hollow converging stream, around the quartz tube 25 to assist gravityy in drawing the metal through said tube- 25, and breaks the stream of metal into small particles, which, when examined, are found to be composed of a homogeneous mixture of lead and copper.

By this method, alloys or homogeneous mixtures of copper and lead containing a lead content of any desired proportion may be made. The described line particles of lead-copper have an extensive use in the manufacture of dynamo brushes, bearings and the like. These particles, each containing from, say, 2% to 20% of lead, may be compressed under heavy pressure, into the form of the desired article. They may then be heat-treated to a point where the particles will cohere, by reason of the union of portions of the lead content of contiguous particles, and form a mass of the desired form which may be readily machined.

If desired, the particles of lead-copper may be mingled with graphite, or any other suitable inert filling material, before being pressed to form, and may be then sintered together in a non-oxidizing atmosphere, so as to produce a porous body capable of absorbing oil. By mixing with the powdered metal. a quantity of Volatile material, such as salicylic acid, the porosity may be increased or controlled. It is possible by this process, therefore, to readily produce articles of an alloy or homogeneous mixture of metals, which, so far as now known, cannot be practically produced by other methods.

The apparatus disclosed herein is claimed in another application iiled of even date herewith, by Harry M. Williams and Victor W. Bihllnan.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form.v it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. A method of making composite metalv particles comprising a mixture of metals which do notl alloy or only partially alloy, which consists in mixing said metals in a molten condition, and atomizing the molten mixture while it is at a temperaturehigher than that at which the metals tend to segregate. i i

2. A method of making composite metal particles comprising a mixture of copper and lead. which consists in mixing copper and lead in a molten condition and atomizing the molten mixture while it is at a temperature higher than that at which the metals tend to segregate.

3. A method of making composite metal particles comprising a mixture of metals which do not alloy or only partially alloy,

which consists .in mixing said metals in a.

container in a molten condition, said container having a nozzle through which the mOltell metal may ow, applying high heat to said nozzle, and atomizing the metal istainer having a nozzle, maintaining said suing therefrom by a stream of aeriform container in a highly-heated environment, 10 uid under pressure. applyinghigh heat to said nozzle, and atom- 4. A method of making composite metal izing the metal issuing therefrom by a 5 particles comprising a mixture of metals stream of aeriform fluid under pressure.

which do not alloy or only partially alloy, l In testimony whereof I hereto aiiiX my which consists in mixing said metals in a signature. container in a molten Condition, said con- HARRY M. WILLIAMS. 

